Method and apparatus for allocating channels in an orthogonal frequency division multiple access system

A method for allocating a frequency to a subscriber station (SS) in handover operation in an Orthogonal Frequency Division Multiple Access (OFDMA) system. In the method, the SS checks safety channel frequencies for a target base station (BS), generates a safety channel frequency request message for requesting allocation of the checked safety channel frequencies, and transmits the safety channel frequency request message. Upon receiving the safety channel frequency request message from the SS, a serving BS allocates frequencies for a requested channel, and transmits an allocation message with the frequency allocation information to the SS. The serving BS transmits a channel allocation request message to the target BS according to the frequency allocation information. Upon receiving the channel allocation request message, the target BS allocates the safety channel frequencies to the SS.